KR20230073292A - Method and extruder for producing high-quality blocks of fixed active media - Google Patents

Abstract

Methods and extruders for producing carbon blocks using poly(vinylidene fluoride) (PVDF) as a binder and an absorbent such as activated carbon are disclosed.

Description

Method and extruder for producing high-quality blocks of fixed active media

The present invention relates to a method and an extruder for producing a block of active media using poly(vinylidene fluoride) (PVDF) as a binder and an active media such as activated carbon.

Blocks of immobilized active media, also referred to as blocks or carbon blocks or monoliths, are filters for water purification applications to remove chlorine, taste, odor and other suspended or dissolved contaminants such as microorganisms and heavy metals from drinking water. has been widely established as Blocks are also used in other applications, such as wastewater purification, catalysts for chemical reactions, electrodes for batteries and supercapacitors, transport, storage, separation and cleaning of liquids and gases.

The blocks are generally made of active media particles or fibers, such as activated carbon, graphite, molecular sieves, metals and derivatives, biocides, heavy metal scavengers, and the like. The block also contains one or more binders, such as polymeric binders, which allow for interconnection between the particles of the active medium. Polymer binders include polyolefins such as polyethylene, polypropylene, and the like; polyvinyls such as polyvinyl chloride, polyvinyl fluoride, polyvinylidene chloride, polyvinylidene fluoride and the like; polyesters such as polyethylene terephthalate, polybutylene terephthalate and the like; It can be composed of almost any thermoplastic material including polyamide and the like. Of these materials, polyethylene and polyester have been the most widely used on the market.

There are two main methods of manufacturing blocks. One is by sinter/compression molding and the other is by continuous extrusion technology. Extrusion is often considered a more cost effective method of producing blocks.

Arkema introduced the Kyblock® series of PVDF polymeric binders to the block industry, which have proven benefits such as low binder loading and improved adhesion to active medium particles, especially to fine particles. In water purification applications, PVDF polymeric binders improve the removal performance of contaminants such as chlorine and heavy metals. PVDF polymeric binders also provide improved performance in other block applications, such as gas transport, storage, separation and cleaning.

The block of the present invention comprises a PVDF polymeric binder. The PVDF polymeric binders include single PVDF polymers, blends of two or more PVDF polymers, and blends of PVDF polymers with other polymers, such as polyethylenes, polyesters and polyamides.

When one or more PVDF polymeric binders are included in the composition of the block, these binders do not allow for drop-in replacement in the methods and equipment used for conventional blocks generally made of polyethylene and polyester binders. Therefore, it is difficult for end users to apply PVDF polymer binders to products, especially products that use extrusion technology to make blocks.

The present invention solves the problem of extrusion when making blocks containing active media particles, e.g., activated carbon and PVDF polymeric binder, improving the ease and throughput of the extrusion process and the quality and performance of the blocks. .

Common problems encountered while extruding blocks using PVDF polymer binders are 1) feeding the fine particle blend of active medium and PVDF binder into the extruder barrel, 2) incomplete curing of the binder, and 3) block locking inside the barrel. (lock up) includes jamming of the extruder. The problem of supplying fine particle blends of materials is primarily related to the flow of the powder material, and PVDF binders tend to impair the flow of the overall powder blend due to the small submicron individual particle size.

Incomplete curing of the block usually occurs in the range of 110 to 180 °C, where the melting temperature of the PVDF polymer binder is generally higher than that of the PE and polyester binders. Curing means that the active medium particles are bonded with a binder. Blocks made using PVDF polymers generally require higher temperatures and/or longer residence times in the heating zone of the extruder. This can produce partially cured blocks when using an extruder of the type with an unflighted short heating zone, for example as disclosed in WO1992017327A2.

Extruder barrel jamming problems are generally due to high friction of the block against the walls of the extruder barrel. This problem arises in particular with blocks comprising small active medium particles of less than 100 μm, preferably less than 20 μm and most preferably less than 10 μm. PVDF polymeric binders are primarily used in blocks such as activated carbon blocks for health claim filters that use small active media particles for heavy metal removal. Jamming problems also occur with blocks comprising PVDF polymeric binders due to the low binder loadings, generally less than 20%, preferably less than 16%. This is because the polymer binder acts as a lubricant and helps minimize friction with the extruder walls.

US2016/0121249 A1 and WO2014055473 A2 teach the use of a thermoplastic binder (PVDF) as a binder in the manufacture of activated carbon block filters and their preparation via compression molding/sintering techniques or via extrusion.

WO1992017327 A2 discloses forming solid composite articles using an extrusion process. An extruder for producing blocks from a blend of activated carbon and a polyethylene binder is disclosed. PVDF is not mentioned as a usable binder. Koslow teaches an extruder that has a short, unwinged heating zone within the barrel, where the heating zone is shorter than the die (cooling) zone. It also teaches that long heating zones do not work because they cause higher friction between the block and the extruder barrel wall, resulting in jamming of the barrel.

The extruder disclosed in WO1992017327 A2 is not suitable for blocks containing PVDF polymeric binders. Short unbladed heating zones generally do not provide sufficient heat transfer to fully cure a block comprising a PVDF polymer binder due to the relatively high PVDF polymer melt temperature of 110 to 180 °C. Therefore, the use of these extruders is limited to very low extrusion speeds.

Jamming or locking problems of blocks comprising PVDF polymeric binders tend to occur with all existing extruder designs, including those disclosed in WO9217327 A2 and those with longer and/or vane-shaped heating zones. Jamming into blocks comprising PVDF polymeric binders can occur due to binder loadings as low as less than 30%, preferably less than 18%, and most preferably less than 12%, since low binder loadings imply that the active medium particles This is because the higher the content, the higher the friction with the extruder barrel. Additionally, many applications, such as advanced CTO water filters and health-claim water filters, require high block densities greater than 0.55 g/cm3, preferably greater than 0.65 and most preferably greater than 0.75. In addition, such blocks generally contain more than 10%, preferably more than 20%, more preferably more than 30% fine active medium particles of less than 100 μm, preferably less than 50 μm and most preferably less than 10 μm. do. The higher block density and the ratio of fine active medium particles both contribute to increased friction with the extruder barrel, which can lead to jamming problems.

A standard extruder, such as that shown in Figure 1, has a vane-shaped feed section and is usually equipped with a gravity dependent feeder to feed material from a feeder hopper into the barrel. Particulate blends of active medium and polymeric binder containing at least 2 wt % of fine particles of active material and/or polymeric binder tend to flow poorly. Poor flow feeds the extruder unevenly. The particle size of the fine particles is less than 50 μm, preferably less than 20 μm, most preferably less than 10 μm (tested at 10 μm or greater with a ro-tap sieve shaker, less than 10 μm with a Microtrac particle analyzer). test). The PVDF binder may contain fine particles of 20% or more, preferably 50% or more and 100% or less. Active media particles can include fine particles, especially in advanced filtration applications where maximizing the accessible surface area of the media is important. Fine particles of typical active media include "activated carbon fine particles", metal reducing agents, bactericides, and the like.

Problems remain in the extrusion of blocks containing PVDF polymeric binders, where using a variety of existing extrusion equipment the continuous feed of the blend of active medium and PVDF binder is inconsistent, the block is only partially cured and/or the extruder The barrel is jammed with the block locked inside.

Applicant of the present invention has now designed a novel extruder that combines a vane-shaped heating zone and a forming zone where the diameter of the barrel is variable and not constant throughout the forming zone. With this novel extruder design, the process of making blocks comprising PVDF polymer binder is improved so that the extruder barrel does not jam.

The present invention relates to a manufacturing process and an extruder, and more particularly to an extrusion process and extruder for producing high quality block products comprising a poly(vinylidene fluoride) polymer binder and an active medium, e.g., activated carbon particles. .

Aspects of the Invention

Aspect 1. An extruder for producing a block of an active medium and a PVDF polymeric binder comprising an extruder barrel comprising a flighted heating zone and an unflighted forming zone, the winged forming zone comprising a cooling section. include,

the heating zone is longer than the forming zone;

The inner diameter “D” of the extruder barrel increases from D ₁ to D ₂ in the unwinged forming zone, and the change rate of the diameter between D ₁ and D ₂ is 0.2 to 1.0%;

wherein the ratio of the length of the heating zone to the length of the forming zone is from 20:1 to 5:4.

Aspect 2. The extruder of Aspect 1, wherein the rate of increase of diameter D ₁ to D ₂ in the forming zone is from 0.2 to 0.9%, preferably from 0.35 to 0.70%.

Aspect 3. The extruder of Aspect 1, wherein the increase in diameter D ₁ to D ₂ is from 0.4 to 0.65%.

Aspect 4. Any of aspects 1 to 3, wherein the change in diameter from D ₁ to D ₂ occurs over 10 to 100%, preferably 30 to 85%, preferably 40 to 75% of the length of the forming zone. one extruder.

Aspect 5. The extruder of any of Aspects 1 through 4, wherein the ratio of the length of the heating zone to the length of the forming zone is preferably from 10:1 to 5:4.

Aspect 6. The extruder of any of Aspects 1 to 6, wherein the heating zone has a length of 0.25 to 2.0 m, preferably 0.5 to 1.5 m, and wherein the heating zone comprises 1 to 10 heating sections.

Aspect 7. The extruder of any of Aspects 1 through 7, wherein the length of the forming zone is from 0.01 to 1 m, preferably from 0.02 to 0.5 m.

Aspect 8. The extruder of any of Aspects 1 to 7, wherein the length of the forming zone is from 0.05 to 0.2 m, preferably from 0.05 to 0.15 m.

Aspect 9. The extruder of any of Aspects 1 through 8, wherein the length of the cooling section is from 0.01 to 1 m, preferably from 0.02 to 0.5 m.

Aspect 10. The extruder of any of Aspects 1 to 8, wherein the length of the cooling section is from 0.05 to 0.2 m, preferably from 0.05 to 0.15 m.

Aspect 11. The extruder of any of Aspects 1 through 8, wherein the cooling section constitutes 20 to 100%, preferably 50 to 99%, of the length of the forming zone.

Aspect 12. The extruder of any of Aspects 1 through 11, wherein the inside diameter “D ₁ ” of the barrel in the vane-shaped section is from 1 to 50 cm, more preferably from 3 to 25 cm.

Aspect 13. The extruder of any of Aspects 1 through 11, wherein the inside diameter “D ₁ ” of the barrel in the vane-shaped section is from 1 to 25 cm, preferably from 3 to 6 cm.

Aspect 14. The extruder of any of Aspects 1 to 13, wherein the extruder further comprises a feeder hopper, wherein the feeder hopper comprises an auger.

Aspect 15. The extruder of any of Aspects 1 to 14, wherein the extruder further comprises an external back pressure device.

Aspect 16. The extruder of Aspect 15, wherein the external back pressure device is selected from the group consisting of a puller, a weight, and a donut device consisting of a spring attached to the block and a finger.

Aspect 17. A method of extruding a block of active medium and PVDF polymer binder,

providing a PVDF polymer binder comprising a PVDF polymer and an active medium;

feeding the PVDF polymer binder and active medium into the extruder of any one of aspects 1 to 14; and

extruding the resulting blend of PVDF polymeric binder and active medium to form a block of fixed medium.

Aspect 18. A method of extruding a carbon block, comprising:

a. providing a PVDF polymer binder and an active medium;

b. providing an extruder comprising an extruder barrel, the extruder barrel comprising a vane-shaped heating zone and an unwinged forming zone, the forming zone comprising a cooling section, wherein the ratio of the length of the heating zone to the forming zone The length ratio is 20:1 to 5:4, the inner diameter “D” of the extruder barrel increases from D ₁ to D ₂ in the forming zone, and the change rate of the diameter between D ₁ and D ₂ is 0.2 to 0.9%. phosphorus, providing the extruder;

c. feeding the PVDF polymer binder and active medium into the extruder; and

d. extruding the blend of the PVDF polymeric binder and active medium to form a block of fixed medium.

Aspect 19. The method of Aspect 17 or 18, wherein the PVDF polymer binder comprising a PVDF polymer and an active medium are blended before being fed into the extruder.

Aspect 20. The method of any one of Aspects 17-19, wherein the temperature of the heating zone is from 20° C. below the melting temperature of the binder to 80° C. above the melting temperature of the binder.

Aspect 21. The method of any one of Aspects 17 through 19, wherein the temperature of the heating zone is from 130 to 260°C, preferably from 170 to 230°C.

Aspect 22. The method of any of Aspects 17 through 21, wherein the binder comprises a VDF/HFP copolymer having a melt viscosity of 5 to 80 kP, preferably 15 to 50 kP.

Aspect 23. The method of any one of Aspects 17-22, wherein the PVDF polymer comprises 5-20wt% HFP.

Aspect 24. The method of any of Aspects 17-23, wherein the combination of active medium and polymeric binder contains at least 2 wt % of fine particles.

Aspect 25. The PVDF polymer comprises individual PVDF polymer particles having an average individual particle size of 50 to 500 nm in size, wherein the size of the agglomerates of the individual polymer particles is 1 to 150 μm, as measured by scanning electron microscopy, preferably The method of any one of aspects 17 to 24, preferably from 3 to 50 μm.

Aspect 26. The method of any of Aspects 17 to 25, wherein the PVDF polymer binder contains at least 20%, preferably at least 50%, and no more than 100 wt% of fine particles.

Aspect 27. The method of any one of Aspects 17-26, wherein the sorbent comprises activated carbon.

Aspect 28. The method of any one of Aspects 17 through 27, wherein the binder constitutes 1 to 30 wt%, preferably 1 to 10 wt%, based on the total weight of the binder and sorbent.

Aspect 29. The method of any one of Aspects 17 through 28, wherein the density of the active medium and the block of PVDF polymer binder is less than or equal to 0.95 g/cc, preferably from 0.50 to 0.90 g/cc, more preferably from 0.65 to 0.85 g/cc. method.

Aspect 30. of Aspects 17 to 29, wherein the extruder produces blocks of active medium and PVDF polymer binder at a rate of 0.5 to 50 cm extruded blocks/min, preferably 0.5 to 30 cm extruded blocks/min. either way.

Aspect 31. The length of the heating zone is 0.25 to 2 m, preferably 0.5 to 1.5 m,

The length of the forming zone is 0.075 to 0.20 m, the cooling section constitutes 27 to 72% of the forming zone, and the expansion ratio from D ₁ to D ₂ along the barrel of the extruder is 0.3 to 0.7%, The method of any one of aspects 17 to 30.

Aspect 32. The method of any of Aspects 17-31, further comprising applying back pressure to the extrusion block.

1 Diagram of a conventional extruder barrel optionally equipped with an internal solid rod to create a hollow cylinder block. The barrel consists of three zones: a feeding zone, a heating zone, and a forming zone including a cooling section. The feeding zone is unheated and vane-shaped, located directly below the hopper of the feeder, and terminating at the edge of the hopper. The heating zone is winged and longer than the non-winged forming zone. The heating zone starts at the edge of the feed hopper and reaches the end of the vane section. In a standard extruder, the diameters of the feeding zone, heating zone and forming zone are constant along the entire length of the barrel. The forming zone is unwinged and generally does not have a heating element. The forming zone starts at the end of the winged section and continues at the end of the barrel. The forming zone generally includes a cooling section in which cooling elements are used.
Fig. 2 Schematic view of an extrusion barrel of the present invention, optionally equipped with an internal solid bar, to create a hollow cylinder block. The barrel consists of three zones: a feeding zone, a heating zone, and a forming zone including a cooling section. This schematic shows a heating zone and a forming zone. The feed section (not shown) is unwinged and is usually unheated but may be heated. The heating zone is vane-shaped and is preferably equipped with a heating element located on the outer surface of the barrel. The forming zone is unwinged and is generally not heated. The cooling section in the forming zone is equipped with a cooling element. It is preferably located on the outer surface of the barrel. In the forming zone, the inner barrel diameter "D" is deformed along the length of the barrel so that the final barrel inner diameter at the exit of the cooling section (D ₂ ) is the initial barrel inner diameter at the beginning of the unwinged zone (D ₁ ). bigger than The deformation of the inner barrel diameter “D” can be gradual or incremental along the entire length of the winged section. The heated zone is the longest zone in the barrel.

All references listed herein are incorporated herein by reference. Unless otherwise indicated, all percentages of composition are weight percentages. Combinations of different elements described herein are also considered part of this invention.

As used herein, “interconnected” means that the active media particles or fibers are permanently bonded together by polymeric binder particles without completely coating their surfaces. During a process called "curing", the binder softens and adheres the active medium particles at specific discrete points, creating an organized porous structure. Blocks produced by the method of the present invention are porous. The block allows the fluid to pass through the interconnected particles or fibers and the fluid is directly exposed to the surface(s) favoring adsorption of the components of the fluid onto the active medium. Because the polymeric binder attaches to the active medium particles only at discrete points, less binder is used for complete interconnection than the binder coated on the active medium.

An extruder for producing a block of active medium and PVDF binder is disclosed.

A method for extruding a block of active medium and PVDF binder using the extruder of the present invention is disclosed.

The present invention provides for the extrusion of blocks of activated media, eg activated carbon, using PVDF as a binder. The extruder has a novel barrel design that is modified compared to existing extruder barrels used to produce blocks. The novel extruder of the present invention makes it possible to successfully extrude a block of active medium and PVDF binder where the block is not locked in the barrel in a jamming event.

The present invention provides a variant of an extruder for extruding a fixed block of active medium, wherein the extruder barrel is such that the modified inner diameter (D ₂ ) of the outlet of the barrel is equal to or greater than the start of the winged section or unwinged section. It is deformed in the forming zone to be greater than the inside diameter (D ₁ ).

extrusion device

The modified extruder barrel includes three zones: 1) a feeding zone, 2) a heating zone and 3) a forming zone comprising a cooling section.

The feed zone is vane-shaped, generally unheated, and receives material from the feeder and conveys the material to the heating zone. The heating zone is vane-shaped, has heating elements, and is the longest zone in the barrel to ensure proper heat transfer and complete curing of the block. The forming zones are winged and some may optionally be heated, but are generally not heated. Within the forming zone the cooling section is unwinged and equipped with cooling elements. The extruder barrel is deformed in the forming zone such that the deformed inner diameter at the end of the forming zone (D ₂ ) is greater than the inner diameter at the beginning of the forming zone (D ₁ ), as shown in FIG. 2 . The ratio of the length of the heating zone to the length of the forming zone is preferably from 20:1 to 5:4, preferably from 10:1 to 5:4, preferably from 8:1 to 6:4.

The absolute length of the barrel and barrel section depends on the thickness of the block. For example, the thickness of a solid cylinder block is the outer diameter of the block, and the thickness of a hollow cylinder block is defined as the difference between the outer diameter of the block minus the inner diameter.

The feeding zone may be 0.1 to 1 m long, preferably 0.2 to 0.5 m long.

The heating zone is longer than the forming zone and may be between 0.25 and 2 m in length, preferably between 0.5 and 1.5 m. The heating zone is equipped with 1 to 10 heating elements, preferably 3 to 5 heating elements. The temperature of the heating element can be set from room temperature to 300°C, and is generally 20°C below the melting temperature of the binder to 80°C above the melting temperature of the binder. The temperature of each element can be independently controlled.

The forming zone may be 0.01 to 1 m long, 0.02 to 0.7 m, preferably 0.05 to 0.5 m long. The length of the cooling section in the forming zone may be 0.01 to 1 m, preferably 0.02 to 0.5 m, 0.05 to 0.20 and even more preferably 0.05 to 0.15 m. The cooling section is equipped with one or more cooling elements. The cooling element may optionally contain a cooling fluid which may be cooled, for example water or another coolant. The temperature of the cooling fluid may be -20 to 90 °C, preferably 0 to 35 °C.

In the forming zone, the inner barrel diameter "D" is such that the final barrel inner diameter at the end of the forming zone is 1.002 to 1.01 times, 1.002 to 1.009 times, preferably 1.003 to 1.007 times the initial barrel inner diameter at the beginning of the forming zone. , most preferably 1.004 to 1.007 times larger. Gradient deformation of the inner barrel diameter D can occur only in the forming zone. The deformation occurs over a length of 10 to 100%, preferably 30 to 85%, preferably 40 to 75%, more preferably 50 to 70% of the length of the forming zone, either in a continuous manner or in one or more steps. transformation can occur. The percentage is calculated as the ratio of the total length of the deformed section to the total length of the forming zone (including the cooling section). The length of the deformed section is measured from the point at which the inside diameter of the barrel first deforms in the forming zone to the end of the barrel at the exit of the cooling section. The gradient deformation makes it possible to compensate for the shrinkage of the die, where the metal alloy shrinks more than the polymeric binder and the extruded active medium to release the pressure built up in the die. After the gradient deformation is complete, the final barrel inside diameter at the end of the forming zone (D ₂ ) is greater than the initial barrel inside diameter at the beginning of the forming zone (D ₁ ). The total increase in barrel inner diameter between D ₁ and D ₂ is 0.2 to 1.0%, preferably 0.35 to 0.7%, most preferably 0.4 to 0.65%. The percent increase is calculated as:

% increase in D = 100*(D ₂ - D ₁ )/D ₁

The inside diameter of the barrel of the wing-shaped section D ₁ is preferably 1 to 50 cm, more preferably 3 to 25 cm. D ₁ can be as large as 100 cm or more. D ₁ may be 1 to 25 cm, 3 to 6 cm or 4 to 5 cm. In the case of a hollow structure, the typical inner diameter of the hollow of the structure is 0.5 to 45 cm, more preferably 1 to 15 cm or 1 to 10 cm.

In one exemplary embodiment, the barrel inside diameter at the winged zone (D ₁ ) is 4.35 cm and is transformed with an incremental gradient of 0.5% to a barrel inside diameter (D ₂ ) at the exit of the cooling section of 4.372 cm. .

Extruders of this type may also be equipped with an external device to prevent the block from coming out of the extruder, which external device helps to create a back pressure to densify the block. It is similar to a typical puller used in the plastics industry by a simple device consisting of a spring and fingers (aka donuts) that resist the speed of extrusion, apply a weight in front of the extrudate, or hold the block and apply pressure proportional to the spring constant of the spring. can be achieved by There are other means of producing a more dense carbon block by creating a back pressure that helps to densify the block that can be used with the extruder of the present invention. Internal design modifications to densify the block, including modifications to the inner diameter of the heating zone, may also be performed to create build-up of material. In this case, the inside diameter of the barrel at the end of the heating zone is smaller than the inside diameter of the barrel at the start of the heating zone.

Feeding equipment, also known as a feeder, is also commonly used in combination with an extruder. They consist of a hopper that takes in bulk material and feeds the material to the extruder at a constant rate. However, typical feeder hoppers, due to their poor flow properties, have problems continuously feeding particulate blends of active medium and polymeric binder containing at least 2 wt % or more of fine particles of active material and/or polymeric binder. The present inventors have now discovered that this problem is eliminated by adding an auger inside the feeder's hopper, which helps to agitate the powder for a consistent feed.

Finally, the extruder can also be set up with an in-line block cutter to help cut the extruded block to a specific length.

With the novel inventive design of the extruder, the problem of jamming when producing blocks containing PVDF polymeric binders is solved. The novel extruder design of the present invention also improves the consistency of the continuous material feed in the extruder barrel and ensures complete curing of the block. Thus, the present invention provides block manufacturers with a highly productive and consistent method for producing blocks of immobilized active media.

The extruder of the present invention is designed to extrude a block comprising an active medium and a PVDF polymeric binder.

binder

Binders in blocks produced using the extruders of the present invention include poly(vinylidene fluoride) PVDF polymeric binders. The PVDF polymeric binder can be a single PVDF polymer, a blend of two or more PVDF polymers, or a blend of a PVDF polymer with another polymer, such as polyethylene, polyester or any other thermoplastic polymer. In some embodiments, the PVDF polymeric binder is a blend of a PVDF binder with another polymer, wherein the PVDF is a major component of the total binder and comprises greater than 50% PVDF polymer, based on the total polymeric binder. In some embodiments, PVDF is not a major component and can be as low as 10% of the total binder content of the block. PVDF polymers are homopolymers of vinylidene fluoride or copolymers of vinylidene fluoride and one or more comonomers. Copolymers have lower melting temperatures and lower modulus than homopolymers. The lower melting temperature of the binder helps alleviate the extruder locking problem.

Preferred PVDF copolymers are tetrafluoroethylene, trifluoroethylene, chlorotrifluoroethylene, hexafluoropropene (HFP), vinyl fluoride, pentafluoropropene, tetrafluoropropene, trifluoropropene. at least one comonomer selected from the group consisting of pen, perfluoromethyl vinyl ether, perfluoropropyl vinyl ether, (meth)acrylic acid, (meth)acrylate esters, and any other monomer readily copolymerized with vinylidene fluoride. and containing at least 50 mol%, preferably at least 75 mol%, more preferably at least 80 mol%, even more preferably at least 85 mol% of vinylidene fluoride (VDF) copolymerized with. The comonomer is preferably hexafluoropropene.

In one embodiment, the vinylidene fluoride polymer is 30 wt% or less, preferably 25% or less, more preferably 15% or less HFP units and 70 wt% or more, preferably 75 wt% or more, more preferably 85 wt% Include VDF units. The PVDF polymer may have 0 to 30 wt%, preferably 5 to 20 wt% of HFP units.

The PVDF used in the present invention is generally produced by means known in the art using aqueous free radical emulsion polymerization, but suspension, solution and supercritical CO ₂ polymerization methods may also be used. Preferably, PVDF is produced by emulsion polymerization.

The surfactant used in the polymerization can be any surfactant known in the art to be useful in PVDF emulsion polymerization, including perfluorinated, partially fluorinated and non-fluorinated surfactants. Preferably, the PVDF emulsions of the present invention are fluorosurfactant-free, and no fluorosurfactants are used in any part of the polymerization. Non-fluorosurfactants useful in PVDF polymerization can be both ionic and nonionic in nature, and include 3-allyloxy-2-hydroxy-1-propane sulfonic acid salt, polyvinylphosphonic acid, polyacrylic acid, polyvinyl sulfonic acid. phonic acids and salts thereof, polyethylene glycol and/or polypropylene glycol and block copolymers thereof, alkyl phosphonates and siloxane-based surfactants. In one aspect, the emulsion polymerization is conducted in the absence of any surfactant.

The latex polymer binder is generally reduced to powder form by spray drying, coagulation or other known methods to produce a dry powder. Powder shape and particle size can be modified by any known process such as milling.

The individual PVDF binder particles generally have an average individual particle size of 5 to 700 nm, preferably 50 to 500 nm, more preferably 100 to 300 nm. In some cases, individual polymer particles may be aggregated into 1-150 μm groupings, 3-50 μm, preferably 5-15 μm aggregates. It has been found that some of these aggregates can break down into individual particles or fibrils during processing into articles. Some of the binder particles are discrete particles and remain discrete particles in the block article being formed. During processing into block articles, the particles are adjacent together in the active medium to provide interconnectivity.

It is important to use as little binder as necessary to hold the active material together, as it exposes more surface area of the active medium and allows it to interact with the fluid during, for example, filtration or adsorption. One advantage of PVDF polymers is that they have a very high specific gravity of at least about 1.75 g/cc, preferably at least about 1.77 g/cc. Thus, the low weight percent of binder required represents a much lower volume percent.

The molecular weight of the PVDF polymer is not particularly limited. A high molecular weight is preferred so that the binder does not flow into the active medium and in one case helps to foul the high surface area of the activated carbon. The melt viscosity of the polymer is preferably 1 to 100 kP, preferably 5 to 80 kP, 5 to 60 kP, most preferably 15 to 50 kP. The melt viscosity of the polymer is measured according to ASTM D3835 by capillary rheometer at 232° C. and 100 sec −1 .

active medium

The active media used are those known to be used in block products. Block products can be used for filtration, eg water filtration, by choosing the right active medium, or they can be used for transport, storage, separation, cleaning of fluids (gases or liquids). Active medium particles are not particularly limited. Examples of active media include, but are not limited to, powdered particles or fibers of activated carbon, graphite, molecular sieves, metals and derivatives, bactericides, heavy metal scavengers, and combinations thereof. One preferred active medium is activated carbon.

The active medium particles of the present invention generally range in size from 0.1 to 3,000 μm in diameter, preferably from 1 to 500 μm and most preferably from 5 to 100 μm. In certain embodiments, the active medium particles have a multimodal particle size distribution, for example, with some particles having an average particle size less than 100 μm and some particles having an average particle size greater than 200 μm. The active medium particles may also be in the form of fibers having a diameter of 0.1 to 250 μm with an essentially unlimited length-to-width ratio. The fibers are preferably chopped to 5 mm or less in length.

The active media fibers or powders must have sufficient thermal conductivity to allow the powder mixture to heat up. In addition, the particles and fibers in the extrusion process have a melting point sufficiently higher than that of the PVDF polymeric binder to prevent both materials from melting and create a continuous molten phase rather than the generally desired multiphase system.

process

The PVDF polymeric binder and active medium can be blended and processed. PVDF polymeric binders are generally in powder form that can be dry blended with the active medium. Preferably, from 0.5 to 35 wt %, preferably from 1 to 30 wt %, more preferably from 3 to 25 wt % of the PVDF polymer binder is used in the block product, based on the total weight of the active medium and PVDF polymer binder. The weight percent of PVDF, based on the total weight of active medium and PVDF polymeric binder, can be from 1 to 10 wt%.

If a very dense block is required, an extrusion process at high pressure may be used. The extrusion process is carried out in such a way that it softens the polymeric binder particles but does not melt and flow to the extent of contacting other polymeric particles to form agglomerates or continuous layers. To be effective in contemplated end uses, the polymer binder remains discrete polymer particles that bind the active medium particles to an interconnected web for good permeability. A solvent that dissolves the binder is not used in the present invention because the individual polymer particles are no longer present in the solvent system as the particles dissolve to form a continuous coating over the active medium particles. Continuous coatings reduce the amount of activated surface area available for active particle interaction with the fluid, which can reduce overall efficiency.

The active medium and polymer binder are formed into block articles in an extrusion process. The blocks of the present invention are formed by an extrusion process. A general extrusion process for carbon blocks is disclosed in US 5,331,037. US 5,331,037 discloses the extrusion of a block made of a polyethylene binder using an extruder with a barrel having a short unbladed heating zone. PVDF is not mentioned as a usable binder.

The polymeric binder/active medium composites of the present invention are generally dry blended and extruded, optionally along with other additives such as processing aids. Continuous extrusion under heat, pressure and shear can produce three-dimensional multiphase profile structures of infinite length. A continuous web of forced point bonds of binder to the active medium particles is formed under extruder conditions.

The extrusion process can produce continuous block structures of any desired diameter and length. Lengths from 1 cm to hundreds of meters can be produced using the right manufacturing equipment. The continuous solid block can then be cut to the desired final length. Blocks can be solid or hollow. The typical outer diameter of the block is preferably 1 to 50 cm, more preferably 3 to 25 cm, although larger diameter structures up to 100 cm or more can be produced using appropriately sized die(s). For hollow structures, typical internal diameters are 0.5 to 45 cm, more preferably 1 to 15 cm or 1 to 10 cm.

An alternative to a single structure is to form two or more structures, a solid rod, and one or more hollow block cylinders designed to overlap together to form a larger structure. Once each annular or bar-shaped block component is formed, the components can be nested together to form a larger structure. This process can offer several advantages over the extrusion of a single large structure. Blocks with smaller cross-sectional diameters can be produced at a higher rate than can be produced with large solid, single-pass blocks. The cooling profile can be better controlled for each smaller cross-section piece. An additional benefit of this concept is that the length of the gas diffusion path through the monolith can be reduced because the spacing between the concentric blocks can serve as a channel for the rapid flow of gas.

Property

The article formed by the present invention is a block structure of a high quality, robust active medium and a binder. The density of the block can be fine-tuned and, for example, can be very high to maximize the volume of active medium to maximize block efficiency.

The extruder of the present invention provides a block having a density of 0.95 g/cc or less. Preferably, the block product may have a density of 0.50 to 0.90 g/cc, more preferably 0.65 to 0.85 g/cc.

The extruder of the present invention provides high productivity due to reduced friction between the composition particles and the extruder walls. The extruder of the present invention can provide production of extruded blocks at a maximum of 0.5 to 50 cm per minute, preferably at most 1 to 30 cm per minute.

The temperature of the heating zone is generally determined by the softening temperature of the binder and is generally from 20° C. below the melting temperature of the binder to 80° C. above the melting temperature of the binder. For example, the temperature is generally 130 to 260 °C, and may be 170 to 230 °C. The temperature may be lower or higher than the example above depending on the polymeric binder.

The novel extruder barrel of the present invention provides continuous extrusion with fine particles using a PVDF polymeric binder that is achieved while minimizing the locking problems experienced when using traditional extruders.

Example:

Example 1

The extruder barrel includes a 0.23 m forming zone with a 1 m winged heating zone, a 0.115 m cooling section. The initial barrel inner diameter of the vane zone is D ₁ = 4.35 cm, and the final barrel inner diameter at the extruder exit is D ₂ = 4.372 cm (0.5% strain). The deformation of the inner diameter occurs along the length of the winged formation zone of 0.172 m. The barrel is equipped with an inner rod for extruding the hollow cylinder block. The rod diameter is equal to the hollow block inner diameter, ID = 1.9 cm. The thread gap is 4 cm (made of CrMoAl).

The formulation contains 8% (by weight) binder (Kyblock® FG-81) and 92% (by weight) 80*325 sized activated carbon from Jaccobi.

The processing conditions are as follows:

A. Mix the binder and carbon in a rotary mixer at low speed for 1 hour.

B. Extrusion conditions: 190℃, 200℃, 150℃, 105℃ (T1 T2 T3 & T4)

The resulting block had a density of 0.75 g/cm (measured as weight/volume after the block had cooled). The line speed for block production is 8 cm/min.

Block density indicates mechanical strength and indicates the stability of the process. The extruder ran for 3 hours without any problems (no locking). This contrasts with the case where the same block composition is run in an extruder using an undeformed barrel with a constant inside diameter of D ₁ =4.35 cm. In the case of the undeformed barrel, the extruder locked up within the first 30 minutes and the block got stuck inside the barrel.

Example 2

The extruder barrel is the same as in Example 1.

The formulation contains 25% (by weight) binder (Kyblock® FX-415) and 75% (by weight) Jacobi's 80*325 sized activated carbon.

The processing conditions are as follows:

A. Mix the binder and carbon in a rotary mixer at low speed for 1 hour.

B. Extrusion conditions: 4 heating zones: 170°C, 180°C, 150°C, 105°C (T1 T2 T3 &T4);

The resulting block had a density of 0.8 g/cm (measured as weight/volume after the block had cooled). The line speed for block production is 8 cm/min.

Block density indicates mechanical strength and indicates the stability of the process.

The extruder ran for 3 hours without any problems (no locking). As in Example 1, this contrasts with the case of an undeformed barrel leading to submersion of the extruder.

Example 3

A powder blend containing 8% (by weight) of binder (Kyblock® FG-81) and 92% (by weight) of Jaccobi's 80*325 sized activated carbon was fed to the extruder barrel using two different feeders. . All binders are considered fine particles, which tend to impair the flow of the whole powder blend in common feeder equipment. In one comparative case using a standard feeder made with a simple hopper design (no auger), the feed of the powder blend into the extruder barrel is inconsistent. The powder tends to adhere to both the hopper wall and the powder itself, creating a "stand-and-go" feed profile. When the hopper of the feeder was modified with an auger, the powder was fed at a constant rate without any inconsistencies. The use of the feeder's hopper modified with an auger is key to consistently feeding formulations containing greater than 2% fines into the extruder. A combination of a consistent powder feed and a modified extruder barrel is required to produce a quality carbon block product.

Claims (32)

An extruder for producing a block of an active medium and a PVDF polymeric binder comprising an extruder barrel comprising a flighted heating zone and an unwinged forming zone, the winged forming zone comprising a cooling section,
the heating zone is longer than the forming zone;
The inner diameter “D” of the extruder barrel increases from D ₁ to D ₂ in the unwinged forming zone, and the change rate of the diameter between D ₁ and D ₂ is 0.2 to 1.0%;
wherein the ratio of the length of the heating zone to the length of the forming zone is from 20:1 to 5:4. The extruder according to claim 1, wherein the rate of increase of diameter D ₁ to D ₂ in the forming zone is between 0.2 and 0.9%, preferably between 0.35 and 0.70%. 3. The extruder according to claim 2, wherein the rate of increase in diameter D ₁ to D ₂ is 0.4 to 0.65%. The extruder according to claim 1, wherein the change in diameter from D ₁ to D ₂ occurs over 10 to 100%, preferably 30 to 85%, preferably 40 to 75% of the length of the forming zone. 2. The extruder according to claim 1, wherein the ratio of the length of the heating zone to the length of the forming zone is preferably from 10:1 to 5:4. The extruder according to claim 1, wherein the length of the heating zone is 0.25 to 2.0 m, preferably 0.5 to 1.5 m, and the heating zone comprises 1 to 10 heating sections. The extruder according to claim 1, wherein the length of the forming zone is between 0.01 and 1 m, preferably between 0.02 and 0.5 m. The extruder according to claim 1, wherein the length of the forming zone is between 0.05 and 0.2 m, preferably between 0.05 and 0.15 m. The extruder according to claim 1, wherein the length of the cooling section is between 0.01 and 1 m, preferably between 0.02 and 0.5 m. The extruder according to claim 1, wherein the length of the cooling section is between 0.05 and 0.2 m, preferably between 0.05 and 0.15 m. 2. The extruder according to claim 1, wherein the cooling section constitutes 20 to 100%, preferably 50 to 99%, of the length of the forming section. 2. The extruder according to claim 1, wherein the inner diameter "D" of the barrel in the vane-shaped section is from 1 to 50 cm, more preferably from 3 to 25 cm. 2. The extruder according to claim 1, wherein the inside diameter "D" of the barrel in the vane-shaped section is between 1 and 25 cm, preferably between 3 and 6 cm. The extruder of claim 1 , wherein the extruder further comprises a feeder hopper, wherein the feeder hopper comprises an auger. The extruder of claim 1 , wherein the extruder further comprises an external back pressure device. 16. The extruder according to claim 15, wherein the external back pressure device is selected from the group consisting of a puller, a weight, and a donut device consisting of a spring attached to the block and a finger. A method of extruding a block of active medium and PVDF polymer binder,
providing a PVDF polymer binder comprising a PVDF polymer and an active medium;
feeding the PVDF polymer binder and active medium to the extruder according to claim 1; and
extruding the resulting blend of PVDF polymeric binder and active medium to form a block of fixed medium. As a method of extruding a carbon block,
providing a PVDF polymer binder and an active medium;
providing an extruder comprising an extruder barrel, the extruder barrel comprising a vane-shaped heating zone and an unwinged forming zone, the forming zone comprising a cooling section, wherein the ratio of the length of the heating zone to the forming zone The length ratio is 20:1 to 5:4, the inner diameter “D” of the extruder barrel increases from D ₁ to D ₂ in the forming zone, and the change rate of the diameter between D ₁ and D ₂ is 0.2 to 0.9%. phosphorus, providing the extruder;
feeding the PVDF polymer binder and active medium into the extruder; and
extruding the blend of the PVDF polymeric binder and active medium to form a block of fixed medium. 19. The method of claim 17 or 18, wherein the PVDF polymer binder comprising PVDF polymer and the active medium are blended before being fed into the extruder. 19. The method of claim 17 or 18, wherein the temperature of the heating zone is between 20°C below the melting temperature of the binder and 80°C above the melting temperature of the binder. 19. The method according to claim 17 or 18, wherein the temperature of the heating zone is from 130 to 260 °C, preferably from 170 to 230 °C. 19. The method according to claim 17 or 18, wherein the binder comprises a VDF/HFP copolymer having a melt viscosity of 5 to 80 kP, preferably 15 to 50 kP. 19. The method of claim 17 or 18, wherein the PVDF polymer comprises 5 to 20 wt% HFP. 19. The method of claim 17 or 18, wherein the combination of active medium and polymeric binder contains at least 2 wt % of fine particles. 19. The method of claim 17 or 18, wherein the PVDF polymer comprises individual PVDF polymer particles having an average individual particle size of from 50 to 500 nm, wherein the size of the agglomerates of the individual polymer particles, as measured by scanning electron microscopy, is , 1 to 150 μm, preferably 3 to 50 μm. 19. The method according to claim 17 or 18, wherein the PVDF polymer binder contains at least 20%, preferably at least 50% and no more than 100 wt% of fine particles. 19. The method of claim 17 or 18, wherein the sorbent comprises activated carbon. 19. The method according to claim 17 or 18, wherein the binder constitutes 1 to 30 wt %, preferably 1 to 10 wt %, based on the total weight of the binder and sorbent. 19. The process according to claim 17 or 18, wherein the density of the active medium and the block of PVDF polymer binder is less than or equal to 0.95 g/cc, preferably from 0.50 to 0.90 g/cc, more preferably from 0.65 to 0.85 g/cc. . 19. The method according to claim 17 or 18, wherein the extruder is capable of producing blocks of active medium and PVDF polymer binder at a rate of 0.5 to 50 cm extruded blocks/min, preferably 0.5 to 30 cm extruded blocks/min. can, how. 19. The method according to claim 17 or 18, wherein the length of the heating zone is from 0.25 to 2 m, preferably from 0.5 to 1.5 m,
The length of the forming zone is 0.075 to 0.20 m, the cooling section constitutes 27 to 72% of the forming zone, and the expansion ratio from D ₁ to D ₂ along the barrel of the extruder is 0.3 to 0.7%, method. 19. The method of claim 17 or 18, further comprising applying back pressure to the extrusion block.

Images